The objective of the program is to conduct bioengineering research, development and clinical implementation of two instruments which continuously monitor oxygen consumption in patients. An adult instrument, already developed, will be clinically evaluated and optimized for use in measuring oxygen and anesthesia gas consumption in the operating room. This unit is a rebreathing type in which all gases are continually circulated past the patient and oxygen and anesthesia gas fractions are kept at a constant set level through feedback controls. A second unit is being designed specifically for use with neonates. It is a non-rebreathing unit to be used in conjunction with a constant flow type neonatal respirator. A special exhalation valve with low dead space, separates the exhaled air, channels it through a dryer and CO2 scrubber into a mixing chamber, where sufficient O2 is added to bring the mixture back up to the inspired oxygen level. The amount of oxygen added to the mixing chamber, controlled by feedback from an O2 sensor, is the amount of O2 consumed by the body. The unit will be tested and evaluated in the laboratory and clinically to determine accuracy and effectiveness.